1. Field of the Invention
This invention relates to forestry equipment, and in particular to a butt plate for a feller buncher for felling and accumulating trees.
2. Discussion of the Prior Art
Felling heads are widely used in the logging industry for accumulating several freshly cut trees in a vertical position prior to laying down the bundle at once, to be transported to roadside by a skidder or forwarder. The felling head is mounted to a heavy duty vehicle, such as a drive to tree or swing to tree wheeled or tracked vehicle, for high efficiency logging.
One type of felling head uses a large saw blade disc having peripheral cutting teeth. The disc is rotated in a horizontal plane below a butt plate, with the teeth exposed at the front of the butt plate. As successive trees are cut, harvesting arms are actuated to pull the tree into an accumulation pocket while at the same time an accumulation arm is withdrawn from the accumulation pocket and then moved behind or brought around the bundle of accumulated trees to add the newly cut tree to the bundle. See, for example, the prior art felling head 10 which is illustrated in FIG. 1.
In FIG. 1, a conventional butt plate 4 is provided over a disc saw 2 operated by a motor 11. In this configuration, the butt plate 4 must be dimensioned to be smaller than the saw radius, limiting the size of the tree accumulation pocket to the small storage area 5 on the butt plate 4 itself. With this arrangement, trees can only be pushed rearwardly to a limited degree, and there is little space for tree storage, and essentially no space for a separate accumulation area, thereby limiting both the size and number of trees which can be accumulated.
Because of these restrictions, various high accumulation butt plates have been developed. For example, butt plates have been developed to include angled ramps which extend over the saw blade to a plateau which provides a larger accumulation pocket, allowing for the accumulation of a larger number of trees and trees of a bigger size. Referring to FIGS. 2 and 3, here a ramp 6 is provided between the butt plate 4 and a substantially flat accumulation area 5. The ramp 6 and accumulation area extend radially from an outer edge of the disc saw 2 toward the motor 11 at the center of the saw 2. The accumulation area 5 extends over at least a portion of the rim of the saw, and the bottom plate 30 of the accumulation area 5 is elevated to achieve this. When using this feller head, the trees are severed and then forced from the butt plate 4, up the ramp 6, and onto the elevated accumulation area 5 by a pivoted harvesting arm. While these butt plates provide a large accumulator, they are difficult to construct as they require multiple bends, machining, bolting and/or welding of the butt plate 4 and ramp 6, as shown in FIG. 3. Furthermore, because the ramp 6 extends radially from the edge of the saw to the motor 11, all accumulated trees must be forced up the ramp 6 to the accumulation area 5. Accumulating trees, therefore, requires a significant degree of force and energy. Additionally, because the accumulation area is flat, once the trees are severed and provided on the accumulation area, they are difficult to keep straight and can slide back and forth on the accumulation plate. Bundles of accumulated trees, therefore, are not stable in the accumulator pocket and can shift during operation.
There remains a need, therefore, for a high accumulation butt plate which is easy and inexpensive to manufacture and which can easily accumulate trees while exerting a limited amount of force and energy.